1. Field of the Invention
The present invention relates to a gas supply unit which is used to supply process gas to be used in a semiconductor manufacturing process and, more particularly, to a compact and lightweight gas supply unit.
2. Description of Related Art
In a wafer treatment operation of a semiconductor manufacturing process, gas is used for etching or the like of a photoresist process (photoresist application, exposure, development, and etching). Accordingly, a gas supply circuit is provided to supply the specific kind of process gas selected from among several kinds of gases to a chamber. The gas supply circuit includes a gas supply line arranged according to the kinds of gases to be supplied, whereby to feed each kind of gas to the chamber through fluid control devices such as a massflow controller and others. Each gas is replaced by use of purge gas such as nitrogen gas because each gas has corrosivity and toxicity. For such gas replacement and further gas exhaust processing, the above gas supply line is combined with a purge gas supply line and a vent line.
To control the flow or exhaust of process gas and purge gas, therefore, the gas supply line needs to have fluid devices such as a plurality of valves and a massflow controller as shown in FIG. 17. These fluid control devices 101 to 108 constituting the gas supply line are unitized for the purpose of achieving a smaller installation area and a shorter flow passage. A gas supply unit 100 is thus constructed of those devices 101 to 108 which are mounted in alignment with each other on a single base member 110 through passage blocks 121 to 128 fixed on the base member 110. Each of the passage blocks 121 to 128 is provided with a V-shaped flow passage as shown in a section view of a block 122 in FIG. 17.
Of the above fluid control devices, a filter 102 would be mounted on the upper surfaces of the passage blocks 121 and 122 as with other fluid control devices. This mounting manner is disclosed in for example Japanese patent unexamined publication No. 11-165012. The case that the filter is mounted to the gas supply unit of FIG. 17 is shown in FIG. 18. The passage blocks 121 to 128 are attached to the base member 110 and the fluid control devices 101 to 108 are mounted on the upper surfaces of the passage blocks 121 to 128. In particular, the filter 102 is constructed of a flat filter 102a disposed in a filter cavity 102b. One side of the filter 102 (an upper part of the filter cavity 102b divided by the filter 102) is communicated with a V-shaped passage 121a formed in the passage block 121 through a passage 102c, and the other side of the filter 102 (a lower part of the filter cavity 102b) is communicated with a V-shaped passage 122a formed in the passage block 122 through a passage 102d. 
Each shape of the passage blocks 121 to 128 is described below, referring to FIGS. 19 and 20; however, these blocks 121 to 128 are identical in shape and therefore only the block 121 is explained. FIG. 19 is a plane view of the passage block 121 seen from above and FIG. 20 is a section view of same taken along the line XX—XX of FIG. 19.
The block 121 is formed with two through holes 131 which are used for securing the block 121 to the base member 110 with bolts. In each through hole 131, a counter bore 131a is formed to receive the head of a bolt. Four screw holes 132 are provided to attach the fluid control device to the block 121 with bolts. The V-shaped passage 121a has an opening part 133 formed with a gasket holding part 133a for holding a seal-gasket.
The above conventional gas supply unit 100, however, has the following problems.
The gas supply unit is usually desired to be installed near a chamber in order to prevent the process gas having a changeable quality from being delivered around through a long pipe line to the chamber. Accordingly, in some cases, the gas supply unit 100 would be not only horizontally installed but also vertically set against a furnace casing of the chamber. In the conventional gas supply unit 100, however, a large number of fluid control devices 101 to 108 are mounted, which results in an increase in weight and length of the gas supply unit 100 itself.
The gas supply unit is generally used so that plural units are arranged in parallel lines or rows. This would need a large space for installation, which makes it impossible to install the units near the chamber. Furthermore, attaching a combination of several gas supply units 100 each being heavy and large would be a difficult work.